I hear you. Remember, she isn't spewing about the R, she is spewing about you taking your kid for a burger.
Breath it in. Respond with a joke. "It was 2 for 1 burger night! Are you trying to make me fat so I won't fit in my skinny pants :)"
Don't tell her she is wrong to be mad. "It sounds like you are angry about this. Would you rather S15 call to check with you first next time? I don't want you to feel like I am going behind your back, we just both had a hankering for a sweet juicy burger."
She is mad because - you are looking like the Good Guy to S15. She doesn't see you as a good dad and happy for the kids, she sees herself as a bad mom. So you being superdad, makes her feel like crappymom and her anger is directed more at that. I see that in my wife as well.
